The present invention relates to a cable inlet device for inserting an optical fiber cable into a chamber or into a container, e.g. into a splice box containing an optical organizer and designed to be placed outdoors or in a buried duct.
In accompanying FIG. 1, which is described in more detail further on below, reference 1 designates an optical cable of known type.
That cable 1 is provided with a strong semi-rigid outer sheath 2 which protects a set of small flexible tubes 3, each of which contains a few optical fibers 4 themselves often embedded in a protective and sealing grease.
In addition, two semi-rigid strength members 5 and 6, e.g. made of aramid fibers, are provided inside the sheath 2, and they are referred to as xe2x80x9cperipheral strength membersxe2x80x9d because they are positioned close to the sheath 2 on either side of the middle longitudinal axis of the optical cable 1.
The free end of the cable 1 is stripped, i.e. the sheath 2, the small protective tubes, and the sealing grease are removed.
The strong outer sheath 2, the strength members 5, 6, the small tubes 3, and the grease coating the fibers 4 are mechanical protections for the optical fibers 4 and they are made necessary because optical fibers cannot withstand any mechanical stress.
Instead of using side semi-rigid strength members 6, 5 to impart strength to the optical cable 1, it is also possible, as shown diagrammatically by way of example in FIG. 1 and in FIG. 10, to use an axial and central semi-rigid strength member 7, and flexible side strength members (not shown), all this being well known to the person skilled in the art.
In the art, the axial and central semi-rigid strength member 7 may be referred to as a xe2x80x9ccentral strength memberxe2x80x9d, and the cable as stripped as shown in FIG. 1 may be said to be xe2x80x9cpreparedxe2x80x9d.
In view of the mechanical weakness of optical fibers, it is necessary for a watertight inlet via which an optical cable can enter a chamber or a container to be provided not only with sealing means, but also with strong means for securing the outer sheath 2 of the cable and its strength members, such as the peripheral strength members 5, 6, or the central strength member 7 and its associated flexible peripheral strength members.
Currently, the Applicant sells an elongate metal securing solepiece that is in the form of a rigid metal bar whose downstream end is provided with a clamping piece for securing the optional central strength member, and whose upstream end is provided with a pair of notches for receiving a clamping collar for clamping the outer sheath of the optical cable against said bar, the upstream notches being followed downstream by two pairs of notches for receiving two securing collars for securing the peripheral strength members.
Once the optical cable has been prepared, then put in place and clamped onto the securing solepiece, the resulting assembly is threaded into the container, and the securing solepiece is fixed by means of screws to a place provided for that purpose in the container. Then, the cable inlet is sealed either by using a heat-shrinkable sleeve, or by pouring in a sealing resin, or else (in other known and analogous devices) by using a conventional stuffing-box sealing device.
Such known cable inlet devices suffer from the drawbacks of being quite voluminous in the longitudinal direction, and of being awkward to use because it is necessary to act positively in the container to fix the securing solepiece therein by means of screws, while access to the inside of the container is often difficult. In addition, the cable inlet sealing is positioned before the place where the outer sheath is secured, so that any external stresses on the cable are applied initially to the sealing device (heat-shrinkable sleeve, sealing resin, stuffing box, etc.), and only then to the sheath securing device. As a result, such a cable inlet device is not very reliable because the sealing device is not always designed to be capable of withstanding external stresses for very long.
An object of the invention is to remedy those drawbacks.
To this end, the invention provides a watertight inlet device for inserting a cable containing optical fibers into a chamber or into a container via an inlet passageway provided for this purpose;
said device being fitted to the cable and secured to the strength members thereof before the cable is inserted into the chamber or container, the outer sheath of the cable further being secured directly on the watertight inlet device and upstream from its sealing means, the watertight inlet device then being received by being threaded into the chamber or container, and being locked therein merely by keying.
The invention provides, in particular, a device as defined above, said device comprising:
at the front: a rigid securing solepiece provided with orifices or slots into which central strength members and/or side strength members of the cable are inserted, each of these orifices or slots co-operating with a clamping member typically acting by a screw being rotated to clamp the strength member(s) that it receives;
at the rear: a nut for clamping a stuffing box, which nut is also shaped to receive a retaining member for retaining the outer sheath of the optical cable; and
between the front and the rear: a sealing tubular body whose front portion engages telescopically into said securing solepiece, means being provided for fixing the sealing body to the securing solepiece in the engaged position, the rear portion of the tubular body co-operating with a sealing ring to form the sealing stuffing box that is complementary to said clamping nut, the stuffing box achieving the sealing by clamping on the outer sheath of the cable;
the sealing body also receiving means for providing the sealing relative to the inlet passageway in the chamber or container, and further including an abutment member which is designed to cooperate with a complementary shape of said inlet passageway to limit the insertion of the device through said inlet passageway, the abutment position then being such that the head of the device emerges inside the chamber or container, keying means then being provided for locking the device in this position.
Advantageously, said clamping nut has an outside shape comprising a plurality of facets, while the rear portion of said passageway orifice is of the corresponding female shape.
Also advantageously, said keying means are constituted by a semi-rigid retaining fork which plugs into an outer annular groove in the cable inlet device, thereby holding it captive in part, the groove therefore emerging downstream relative to said inlet passageway when the device is inserted to its abutment position. /